Recent revisions

Removed the natgrid references from the cookbook and changed calls to matplotlib.griddata to scipy.interpolate.griddata (as the matplotlib griddata function is deprecated). Also, updated the cookbook to reflect these changes.

I've put together a flatpak of escript to make it easier for end users to install it on their machines. To easily install escript on any linux distro, install flatpak and flatpak-builder from a repository and then type

flatpak-builder [some build directory] [path to escript.json]

where escript.json is the file I have uploaded in this commit. Note that this will require flatpak version 1.2.0 or higher, so if you want to try this out on debian you will need to install flatpak and flatpak-builder from stretch-backports. Then to run, type